Regulating means for centrifugal compressors.



O. BANNER.

REGULAUNG MEANS FOR CENTRIFUGAL COMPRESSORS.

APPLlCATlON ELLED OCT.25. l9l2.

Patented Sept. 28, 1915.

OTTO BANNER, OF EASTON, PENNSYLVANIA, ASSIGNOR T0 INGERSOLL-RAND COMPANY OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

REGULATING MEANS FOR CENTRIFUGAL COMBRESSORS.

Application filed October 25, 1912. Serial No. 727,649.

To all whom it may concern:

Be it known that I, OTTO BANNER, a sub ject of the German Emperor, residing at Easton, in the county of Northampton and State of Pennsylvania, have invented acertain new and useful Improvement in Regulating Means for Centrifugal Compressors, of which the following is a specification.

This invention relates to centrifugal compressors and more particularly to regulating means for such compressors.

Although centrifugal compressors can be designed to furnish air at practically constant pressure through quite a large range of volume there is a certain limit, according to the design of the compressor, below which the volume of the air, taken from the compressor, can not be decreased. Below this limit, the air does not flow continuously through the compressor but the pressure backs up in certain places and forces its way back through the impellers causing a pulsation or pumping, as it is called.

The object of the present invention is to provide a compressor and a regulating means for it which will allow the compressor to be operated through a large rangeof volume below this so called pumping limit.

With this object in view I have devised a regulating means, practical embodiments of which are shown in the accompanying drawings in which:

Figure 1 shows a partly diagrammatic side elevation of a compressor provided with my regulating means. Fig. -2 shows a similar view of a further refinement of the idea.

As shown in Fig. l the compressor comprises a centrifugal compressor 1 which may be of any desired construction driven by a motor 2. Air or other gas is taken intothe compressor through the inlet pipe 3 and dis-' charged through the exhaust pipe 1. Abovethroat 6 and its discharge opening 7 which.

varies in proportion to the amount of fluid passing through the tube. This varying difendsof a valve operating cylinder 10 in which slides a piston 11 which has a constant pressure toward the back end of the cylinder, into which leads the pipe 9, from a spring 12. This spring 12 is of such a strength that the piston 11 will take a position in the cylinder depending on the excess of pressure in'the pipe 9over that in the pipe 8. Attached to the piston 11 is a rod 13 which is secured by a link 14 to a lever 15. This lever 15 is secured to a shaft 16 on which is mounted a throttle valve or damper 1-7 placed across the opening of the inlet pipe 3 and adapted to open or close it according to its position, the connections to the piston 11 being such that the throttle valve tends to close as the difference in pressure in the ends of the cylinder 10 and ac cordingly in the throat and the discharge of the Venturi tube 5 is decreased.

A set screw 18 adjustably limits the rearward movement of the piston 11 and consequently the final position of the throttle valve 17. From the throat and discharge opening of the Venturi tube pipes 19 and 20 lead also to. the front and rear ends of a sec- Specification of Letters Patent. Patented Sept. 28, 1915.

0nd cylinder 21 provided with piston 22 and 26 in a pipe 27 which opens to the atmos- 'phere from the discharge pipe 4 of the compressor. This valve is arranged to open upon rearward movement of the piston 22 vdue to a decreased difference in the pressure in the throat and discharge opening of the Venturi tube. An adjustable set screw 28 also limits the movement. of the piston 22 and the valve 25.

In operation, the difference in pressure in the throat and discharge of the Venturi tube and the strength of the spring 12 are so adjusted that the piston 11 will be maintained in its extreme forward position and the throttle valve 17 remain in a fully open position as long as the amount delivered by the compressor-through the Venturi tube is above the pumping limit of the compressor. As the demand on the compressor falls below this limit and the difference in pressure in the Venturi tube is decreasedjthe piston 11 that the throttle valve is allowed to close only a certain amount, which is determined by the position of theset screw 18. Here the valve 25 takes up the regulation. The spring 23 is of such a strength that the piston 22 will be maintained in its forward position and the valve kept closed until the throttle valve 17 has been closed to the desired extent by the piston 11.- At this point the spring 23, will overcome the difference in pressure in the two ends of the cylinder and will open the valve 25 an amount proportionate to the decrease of the demandallowing any excess of air over the demand to be exhausted to the atmosphere. Itwill thereforebe seen that the regulation of such compressor takes place in three stages. Above the pum'pinglimit the ordinary speed regulation is employed. When the pumping limit is reached an additional regulation is added in the form of a device for automatically throttling the intake thus decreasing the amount of air taken-into the com n'essor and preventing pumping. \Vhen the practical limit of this throttlingregulation is reached the compressor will run at constant speed and with constant gross delivery, but a portion of the air delivered to the discharge line is exhausted to the atmosphere.

' In Fig. 2 a further refinement is added along the lines of the mechanism disclosed in my 'copending application, Serial No. 727,650, filed October 25th, 1912, which decreases the power used in the-third stage of regulation. In thisform the compressor is provided at its forward end with a turbine wheel 28 provided with blades 29, which is directly mounted on the shaft of the compressor. Instead of the air being allowed to escape to the atmosphere when valve 25 is open it is passed through a pipe '30 and directed by one or morev nozzles 31 on the blades of the turbine wheel. From there the air passes directly into the first .impeller 32 of the compressor and again travels through the compressor. In this way the compressed air in thedischarge line, which is allowed to escape in the first form, is made to perform useful work in actuating the turbine wheel 28 thus diminishing the loadon the motor driving the compressor a-n'amount proportionate to the air allowed to escape from the discharge line andpass through the turbine It is 'to be understood that the present showing and description discloses only certain specified modifications of my invention and other forms and modifications are included in the spirit and scope of the inventionas expressed in the claims.

What I claim is:

1. In combination with a centrifugal com pressor, having an intake and a discharge line, a demand measuring device in said discharge line and means operated from said demand measuring device. for serially choking the intake of the compressor and exhausting the disclmrge-l ine of the compressor as the demand decreases.

2. In combination with a centrifugal compressor having an intake and a discharge line. a demand measuring device. in said discharge line. a valve for choking said intake, means operated from said measuring device to close said valve as the demand decreases, a valve for exhausting said discharge line. and means,operated from said measuring device to open said discharge line valve as the demand decreases, said discharge line valve operating means operating at a lower demand than said intake choking device.

3. In combination with a centrifugal compressor having an intake and a discharge line, a demand measuring device in said dis charge line, an intake choking valve having a motor operated from said demand measuring device arranged to close said valve as the demand decreases below a predetermined point. and a discharge exhausting valve for said compressor, having a motor arranged to open said discharge valve at a demand lowerthan that at which said intake closing motor operates. 1

4. In combination with a centrifugal compressor having an intake and a discharge line. a Venturi tube, a valve for closing the intake'of said con'ipressor, a valve for exhausting the discharge of said compressor, motors for operating said valves. comprising cylinders and pistons therein, and con nections from the said tube to one end of each of said'cylinders and from the discharge of said tube to the other ends of said cylinders, the piston in the intake'valve motor being arranged to operate at a greater line, a demand measuring device in said dis-.

charge line, means operated from said demand measuring device, for serially chok ng the intake of the compressor and exhausting the discharge line of the compressor as the-- demand decreases, a fluid pressure eng ne operatively connectedW-ith said compressor,

and means for conveying the exhaust'fluid from the discharge line tosaid engine.

6. In combination with a centrifugal compressor having an intake and a discharge means operated from said measuring device to close said valve as the demand decreases,

a valve for exhausting said discharge line, means operated from said measuring device to open said discharge line valve as the demand decreases, said discharge line valve operating means ope 'ating at a lower demand than said intake choking device, a fluid pressure engine operatively connected with said compressor, and means for conveying the exhaust fluid from the discharge line to said engine.

7. In combination with a centrifugal compressor having an intake and a discharge line, a demand measuring device in said discharge line, an intake choking valve having an operating motor operated from said demand measuring device arranged to close said valve \vhenthe demand decreases below a predetermined point, a discharge exhausting valve for said compressor having an operating motor arranged to open said discharge valve at a demand lower than that at which said intake closing motor operates, a fluid pressure engine operatively connected with said compressor, and means for conveying the exhaust fluid from the exhaust line to said engine.

8. In combination with a centrifugal conipressor having an intake and a discharge line, a V enturi tube, a valve forclosing the intake of said compressor, a valve for exhausting the discharge of said compressor, motors for operating said valves comprisingcylindcrs and pistons therein, lluid con nection from the throat of this Venturi tube to one end of each of said cylinders and from the discharge of said tube to the other ends of said cylinders, the piston in the intake valve motor being arranged to operate at a greater difference in pressure in the ends'of its cylimler than the piston in the discharge valve motor, a fluid pressure engine operatively connected with said conip-ressor, and means for conveying the exhaust fluid from the discharge line to said engine. Y v i In testimony whereof, l have hereunto set my hand.

OTTO BANNER.

Witnesses I PAUL How-MAN,

F. A. Porn. 

